The present invention relates to a hand held, motorized depilatory device for removing unwanted skin hair, and more particularly, to a revolutionary concept and mechanically correct design to pluck out skin hair, utilizing a novel mechanism to spirally align coupled-tweezer elements.
The prior art of motor-powered depilatory devices for removing skin hair is based on a well-known concept disclosed in a patent covering an earlier mechanical device, Swiss Patent 268,696 to Fischer. There, a helical spring is arched, to provide spaces between loops of its convex side, and the spring is placed on the skin, under slight pressure, and rolled, in the direction of hair growth. The rolling motion of the helical spring causes hairs, which become trapped in the spaces, between the coil loops, on the convex side, to be plucked, when these spaces close, on the coil spring concave side.
U.S. Pat. No. 4,524,772 to Daar, et. al., discloses an arched, helical spring, which is provided with high speed, rotational motion via motor-driven couplings, connected at its ends. The contact between the helical spring wire and individual hairs is essentially point-like. A hair that is caught between the closed spring loops may be released before the plucking operation has been completed, which results in inefficient plucking and unnecessary pain.
Once a hair becomes trapped between closed helical spring loops, continued application of rotational force causes the spring to xe2x80x9cwind upxe2x80x9d, since it is composed of flexible wire material, yet the hair is still in place. As the spring continues to xe2x80x9cwindxe2x80x9d, the pulling tension applied to the hair increases until the necessary force is developed for plucking. Because a finite interval is required for this force to be developed, the user is subjected to an increased pain level.
The helical spring may break during use, due to the continuous bending stresses applied to it, creating a hazard to the user, as the spring is in direct contact with the skin.
In addition, a transverse deflection of hairs takes place, due to lateral movement of the spaces between the helical spring loops, which rotate in spiral fashion. Therefore, shorter hairs tend to escape the traps, created by the helical spring loops.
In U.S. Pat. No. 4,575,902 to Alazet, there is disclosed a depilatory device, comprising a series of adjacent, closely-spaced hair-plucking discs, driven by an electric motor, housed within a casing. The discs are periodically deformed during their rotation, such that adjacent ones, thereof, are pressed together to pluck hairs, which may have become trapped between them, when the unit is passed over the skin. When the discs are pressed together, the external hair-traps, thus formed, capture mainly hairs located in the center of the device""s rotational path. The short hairs, located on the peripheries of the rotational path, are not trapped and consequently, not plucked.
In U.S. Pat. No. 4,575,902 to Alazet; U.S. Pat. No. 5,041,123 to Oliveau, and U.S. Pat. No. 4,960,422 to Demeester, simultaneous closing of blades is complicated and extremely difficult to ensure, while maintaining a uniform gripping force in all hair-traps. These patents describe devices, in which, parallel-positioned plucking blades or disks are fixed, relative to the rod, which carries them. Typically, cam driven motion of the rods causes the blades to close one against the other. On application of force, sufficient gripping force will be attained by some of the blades, while other blades will not be subjected to sufficient force and will remain open.
The difference in plucking-blade response to a given mechanical force is primarily a result of non-uniformity in the production of the unit elements. As a certain level of non-uniformity accompanies all production, correct and efficient performance requires finding a method to decrease, or preferably, eliminate the detrimental effects of non-uniform production.
In order for the blades to close, further force must be exerted, which causes excessive stress on the blades, which closed first. Excessive stress on the blades typically causes hair to be cut instead of plucked. In addition, a certain percentage of plucking attempts is unsuccessful. Each time hairs are pulled, without plucking the hairs, the result is increased pain, increased energy consumption, (which is particularly significant in the case of battery-operated devices), increased noise and excessive wear and tear of parts.
Therefore, it would be desirable to provide a superior power-driven depilatory device, which provides a drastic improvement in the ratio of plucked to cut hairs, while minimizing pain associated with the interval between grasping and plucking of individual hairs.
It would also be desirable to provide a depilatory device, which would reduce noise, and therefore be less frightening to the user.
Furthermore, in the prior art, the depilatory devices were designed, so that to be effective, the user had to hold the device substantially perpendicular to the skin surface, at many times, a most awkward position to work in.
Therefore, it would also be desirable to provide a depilatory device, whose design allows the user to efficiently utilize the device at additional contact angles with the skin surface. This would allow the user to easily maneuver the device, so as to remove hair efficiently, in hard-to-get-to areas, such as the back of the knee joint area. In addition, such a design would also allow the user to easily view the area to be depilated, which was most difficult to do in prior art devices.
Additionally, it would be desirable to provide a depilatory device, whose mechanically correct design will lead to an efficient distribution of the applied force and thereby reduce excessive wear of parts and improve the plucking efficiency.
Accordingly, it is a principal object of the present invention to overcome the above-mentioned disadvantages and provide a hand-held, motorized depilatory device for removing unwanted skin hair, utilizing a mechanically correct design employing a novel mechanism to spirally align coupled-tweezer elements.
In accordance with a preferred embodiment of the present invention, there is provided a motor-powered depilatory device comprising:
a manually-held housing;
motor means disposed in said housing; and
a hair-plucking assembly, exposed through an opening in said housing, and coupled to said motor means, said hair-plucking assembly containing a right hand actuator element and a left hand actuator element, identical in construction, each carrying opposing tweezer elements, which fit together in interleaved fashion, arranged to define hair-traps,
said hair-plucking assembly being rotatable about a central shaft and operable to close and open said hair-traps by a system of cams and springs.
Hair-traps are developed by a series of tweezer elements, mounted circumferentially on said hair-plucking assembly. Each of said actuator elements has a pair of carrier arms, containing slots, in which said tweezer elements are mounted. The actuator elements are arranged to provide slots for installation of a plurality rows of tweezer elements, arranged in a staggered, rather than tandem arrangement.
The actuator elements, in the preferred embodiment of the present invention, are made of plastic and are simply designed, and identical in construction, making them inexpensive to manufacture, via injection molding.
On each actuator element, adjacent to the carrier arms are cams, on which are positioned cam followers that are supported by cam follower holders. Two sets of cam followers are held, one at each end, formed by the actuator elements, and are prevented from rotating by an actuator spring. The actuator spring is held in place within a slit, in the body of the appliance, which prevents it from rotating with the hair-plucking assembly. The actuator spring exerts pressure on the ends of the central shaft, which is relayed to the cam follower holders, the cam followers, and through the cams to the actuator elements.
The actuator spring transfers gripping force to the tweezer elements, where gripping force is the specific force required to grip and pluck the hairs. Gripping force is required only at specific points in the operating cycle. During the remainder of the cycle, a retaining spring mounted on the shaft provides the force needed to re-open the hair-traps.
In operation, when the hair-plucking assembly receives rotational motion, the cam followers roll on the cams and when they reach a projection on the cam surface, the actuator elements are pushed one against the other, thereby causing the tweezer elements, of opposing actuator elements, to engage, forming hair-traps on all rows of tweezer elements, simultaneously. Thus, hairs are plucked out, during the rotational motion of the hair-plucking assembly. The cam followers continue rolling along the contour of the cams, eventually arriving at a depression in the cams. At that point, the retaining spring is free to return the actuator elements, as well as the tweezer elements situated on them, to their initial positions, thereby opening the hair-traps, allowing the plucked hair to be released.
Cams are located at each end of the hair-plucking assembly, and are arranged as a set in a circular arrangement, which effectively constitutes a continuous cam arrangement. In the preferred embodiment, a set of four cam followers, arranged perpendicular to each other, is positioned on each set of cams. This correct mechanical design allows the force applied by the actuator spring to be evenly distributed on all points of the cams of the actuator, surrounding the shaft. Thus, the force per point is smaller than in prior art devices, reducing the stress per point, which is an important factor in reducing accelerated wear of parts and excessive noise.
Each tweezer element comprises two wing segments and a central portion. In one of its embodiments, the tweezer element, in its central segment, has formed thereon protrusions. A tweezer element, when engaged, is able to rock slightly around the protrusions. This arrangement permits self-alignment of the tweezer element, thereby enabling uniform distribution of gripping force among all hair-traps. In another embodiment, instead of a protrusion on the tweezer element, a swivel ridge is formed on the wall of the slot, in which the tweezer element is mounted.
The assembly procedure of the hair-plucking assembly is quite simple and rapid. The tweezer elements are snapped into position easily, and held in place by a tongue, or other mechanical means, such as the hair-guide unit, utilized in one of the embodiments.
The tweezer elements are arranged around the hair-plucking assembly, in such a way, that the tips of each tweezer element can engage with the tips of each of two adjacent tweezer elements, so that the tweezer elements form a continuous spiral around the circumference of the assembly. The tweezer elements are able to rock slightly around said protrusions, and thereby align themselves relative to fixed points, provided by a fixed tweezer element. This novel mechanism ensures that all tweezer elements close simultaneously, developing an appropriate equal gripping force, despite inaccuracies in manufacture.
The inventive hair-plucking assembly insures all the hair-traps close simultaneously during a revolution of the hair-plucking assembly, with no excessive applied force being required. Quality of hair plucking is thereby improved, where quality of plucking is defined as the percentage of hairs plucked versus percentage of hairs cut. In prior art devices, excess applied force led to an increase in the number of hairs cut rather than plucked.
The staggered arrangement of tweezer elements contributes to a much more even treatment of the skin surface, and to an increase in the speed of removal of hairs from a given area, thus leading to reduced energy consumption per unit of time.
A further advantage of the present invention is the operation of the actuator elements by the continuity of the cams. The use of four cam followers per cam, eliminates the need to jump from one cam to another, as is the case in, other hair plucking appliances. This configuration decreases noise levels, reduces energy requirements and reduces wear and tear of the device.
Other features and advantages of the invention will become apparent from the drawings and the description contained herein below.